1. Field of the Invention
The invention relates to a PIFA/monopole hybrid antenna and a mobile communications device provided with the PIFA/monopole hybrid antenna.
2. Description of the Related Art
Internal antennas are increasingly popular and widely used in mobile communications devices (e.g. cellular phones). Recently, planner inverted F antennas (PIFAs) and monopole antennas have become available.
A planner inverted F antenna is required to be spaced apart from a circuit board of a mobile communications device at a predetermined vertical distance, and no electronic components are allowed between the planner inverted F antenna and the circuit board. However, the predetermined vertical distance is limited by the thickness of the mobile communications device which is generally small. As a result, the performance of the antenna measured in bandwidth, radiation efficiency, and gain is hindered.
Differing from PIFAs, a monopole antenna is required to be spaced apart from the electronic components of the circuit board of a mobile communications device at a predetermined horizontal distance. That is, a clearance zone is required between the monopole antenna and the electronic components of the circuit board to avoid negative disturbances to the monopole antenna. Therefore, the dimensions of monopole antennas are suitable for slim type communications devices. In operation, however, the monopole antenna has a problem of a higher specific absorption rate (SAR) in the human body and is more susceptible to phantom effect.